Turnout estimates are notoriously unreliable. But as the dust settled around America's polling booths on Wednesday, it was broadly agreed that voters had shown up in record numbers to participate in the most electrifying US presidential election for a generation.

Preliminary projections, based on reporting from 83% of precincts nationwide, indicated that more than 131 million Americans, or 64% of eligible voters, cast a ballot on Tuesday.

If accurate, that percentage figure narrowly beats the previous modern high of 63.8% set in the 1960 contest between John F Kennedy and Richard Nixon. It is close to the all-time 1908 record of 65.7%, ratcheted up in the contest between William Howard Taft and William Jennings Bryan.

In terms of gross numbers, Tuesday's figure of 131 million voters also trounced the previous record, set in the 2004 contest between George Bush and John Kerry, of 123.5 million.

The rise in turnout was attributed to unprecedented get-out-the-vote efforts by both Democrats and Republicans involving thousands of grassroots volunteers and automated email, text and telephone calling (robo-calling).

The novelty of the first ever major-party black presidential candidate and first ever female Republican vice-presidential candidate also raised voter interest. Advertising expenditure, and the duration of the campaign, broke previous records. But anger over the economy appears to have been the biggest motivator of all.

Campaigning via the internet, used to telling effect by Barack Obama's supporters, reached unusual numbers of younger voters, who turned out in force. According to exit polls, roughly one in 10 voters said this was the first time they had taken part in a presidential poll. About seven in 10 voted for Obama. Overall, six in 10 new voters were under the age of 30.

Significantly, one in five of these first-time younger voters was black, and one in five was Hispanic – a disproportionately large participation rate in terms of these minorities' overall population share. Like new voters who identified themselves as independents, these groups went overwhelmingly for Obama.

The election commission reported more than 100,000 complaints about voting irregularities. These ranged from broken voting machines and long queues, to the distribution of rogue leaflets at colleges warning students they would lose grant money if they voted.

But although some of yesterday's biggest difficulties, involving the breakdown of optical scanners in three-dozen precincts, were reported in Florida, there was no repeat of the "hanging chad" fiasco that paralysed the 2000 count. Nor were pre-poll fears of mass disenfranchisement of minority voters realised on the day.

On Wednesday morning, only two states – North Carolina and Missouri – remained too close to call, although there were several undecided congressional races.

Officials said early voting, now permitted in 34 of the 50 states, had also boosted overall turnout. In all about 29 million people voted before election day, a little over 20% of the total.

Turnout analysis answered some outstanding questions left over from the campaign. One issue - whether Democratic supporters of Hillary Clinton would switch their votes to Obama – was resoundingly answered in the affirmative. In the event, nearly nine out 10 of Clinton's primary supporters backed their party's nominee.

Likewise, the so-called Palin effect, a reference to the impact on voters of the surprise choice of Republican vice-presidential candidate Sarah Palin, was illuminated at the polling booths. Four in 10 Republicans said Palin was an important factor underpinning their vote. But similar numbers of independents and moderates said her candidacy had pushed them towards Obama – not the effect that John McCain intended.

After this tumultuous, highly publicised and mould-breaking election, one big question remained unanswered: what, if anything, could possibly persuade the 36% of Americans who did not vote to take part in future?